Metal beverage cans usually have a pull tab (working as a lever mechanism) to allow for the opening of the can along a pre-determined shallow groove. This design allows venting the excess pressure in the can when it is opened. As the tab is lifted, first a vent score is severed, allowing the gases in the can to be released, and then the aperture score is ruptured, which defines an aperture through which the contents of the beverage can may be dispensed. The groove has the shape of a non-closed loop, so that when pressure is applied by the lever to rip the metal along the groove, the metal tab that is ripped off remains attached to the top of the can, even when the lever is returned to its original position.
With existing cans, a permanent opening is formed by these manipulations, so that the contents of the can may be drunk, but on the other hand carbon dioxide may escape and spills may occur.
Patents U.S. Pat. No. 4,784,283 and U.S. Pat. No. 5,810,189 disclose beverage cans that include a spring-loaded tab inside the can that is configured to reclose the drinking aperture after the can is opened for the first time. However, for a carbonated beverage can, pressure is built up in the can because of the gases. The pressure decreases as the amount of liquid in the can decreases, but the pressure can be quite high initially: depending on the temperature of the liquid, this pressure can be between 3 and 4 bar. Such a high pressure on a closing surface of e.g. 2.5 to 3.5 cm2 results in a large force that needs to be counteracted when opening the can for drinking when the can still contains a large amount of beverage.
Patent application US 2008/0314904, with inventor Perra, discloses a closing device for a food product container, more particularly a drink container, that includes a wall part provided with an opening and a shield member sealing the opening. The shield member is displaceable between a first, closed position sealing the opening in the wall part and a second, opened position leaving the opening at least partly open. The shield member is provided with a locking member securing the shield member in the first, closed position, and the shield member oriented in the first, closed position can be unlocked by displacing a locking member. The operations of unlocking and opening a (drinking) opening are separated such that both operations can be optimized independently of each other. The food product container can be used for carbonated drinks, such as sparkling water. In this case, pressure is built up in the drink container because of the gases. In an embodiment, a closing device with a gas passage is disclosed that acts as a relief valve to decrease pressure in the drink container when it is opened for the first time. Instead of for carbonated beverages, the food product container can also be used for other food articles, such as for example non-carbonated beverages, instant soup, instant coffee, oil, honey, sauces, dairy products such as milk or yoghurt, et cetera.
Patent application WO 2007/147542 A1 discloses a closing device for beverage cans, wherein the device comprises an opening tab provided in a wall of the beverage can, an opening element for pressing the opening tab inwards, and a fixing device for detachably fixing the opening tab to said wall of the beverage can.